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February 1953 E-854
United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
TESTS OF SEVERAL INSECTICIDES FOR THE CONTROL
OF RESISTANT HOUSE FLIES^
H. G. Wilson, R. S. Anders, and C. N. Husman?/
Division of Insects Affecting Man and Animals
Early in 1949 studies at the Orlando, Fla., laboratory of the Bureau
of Entomology and Plant Quarantine showed that residual treatments of
DDT and methoxychlor were no longer effective in controlling house
flies (Musca domestica L.) in dairy barns (Gilbert, Wilson, and Coarsey 1),
Laboratory tests with the flies from the dairies indicated that the ineffec-
tiveness of the treatn ents was due to their increased resistance to these
insecticides. In subsequent tests these resistant strains of flies were
controlled satisfactorily with residual applications of chlordane, lindane,
or dieldrin, and also by frequent space spraying with lindane, dieldrin,
or pyrethrun. plus piperonyl butoxide. At the end of 1949, therefore,
there was no great concern over the control of DDT-resistant house
Early in 1950 residue tests in barns were started with the insecti-
cides that had given satisfactory control of flies in 1949, as well as
with toxaphene, heptachlor, and a new material, CS-708. At first
most of the treatments were moderately to highly effective, but as the
season advanced all declined in effectiveness and by late summer none
provided satisfactory control.
Extensive tests in dairy barns were also made in 1950 with space
sprays of lindane, dieldrin, allethrin, and pyrethrum. Lindane and
pyrethrum plus piperonyl butoxide each gave control of flies in one
barn, but elsewhere all the materials gave generally poor results.
1_/ This work was conducted under funds allotted by the Department
of the Army to the Bureau of Entomology and Plant Quarantine.
2/ The writers acknowledge the assistance of W. V. King and
W. C. McDuffie, under whose supervision this work was done, and
also of A. A. Whipp, of the California Spray-Chemical Corporation,
in conducting the residue phase of these studies and furnishing the
: house fl
1 a la -ling pi
at would act a*
: house f. als
to I f]a., lab( . -
al tests, ho. iual treatments of
'. of D of DD square foot failed to
measura tion of fly populations.
Iual- and : DDT and lindane,
alone ai rcial s , to dete their ef:
against the hi^ sistant flies in several local dairy bar -re D.
an< lorinated hydrocarbon ins- ies had been used for ar
barns had been used
of a t:
Applications were made at the uniform rate of 1 gallon of spray per
1,000 square feet, the concentration being varied to give the desired
dosages per square foot. Sprays were applied at close range with a
power sprayer at a pressure of about 75 pounds per square inch. All
treatments were applied as emulsions except the methoxychlor-lindane
combination, which was a wettable-powder suspension.
Estimates of fly populations were made in each barn at least 2 days
before treatment and at various intervals thereafter to determine the
effect of the treatments. The estimates were based on counts of flies
alighting on hardware cloth laid over two petri dishes containing equal
parts of malt extract and water as an attractant. Several counts were
taken at three locations in each barn, the flies being disturbed after
each count. Results of the tests are given in table 1.
Lindane alone gave excellent immediate reductions in two dairies
but was relatively ineffective in two others. Three of these dairies
showed poor control after 3 days, but the fourth exhibited good control
at both the 3- and 7-day counts. Lindane with synergist RE-1901 gave
better immediate control than lindane alone, but none of the treatments
were highly effective for more than 1 week. In one dairy the treatment
remained fairly effective through 2 weeks, but a second application
failed after 1 week. In another barn a second treatment showed im-
mediate results considerably better than the first, but was effective
for only 1 week. The special lindane formulation (RE-2035) was about
as effective as the best treatment of lindane alone.
The mixture of methoxychlor and lindane was about equal to lindane
alone. Two of three applications gave good immediate control, but
neither was satisfactory after 3 or 7 days.
In one test DDT alone gave relatively poor immediate control and
was completely ineffective thereafter. In two of three tests DDT plus
a synergist gave better immediate control than DDT alone, but control
after 3 days was unsatisfactory. The same synergist with toxaphene
was relatively ineffective.
Treatment of Premises
Following the failure, in 1950, of both residual and space-spray
treatments of various insecticides to control house flies, a series of
tests were made to determine whether satisfactory control could be
obtained by spraying the barns and premises, usually an area of about
2 acres, with the same insecticides. The sprays were dispersed inside
and outside of all buildings and over the barnyards, with a Microsol
sprayer mounted on a jeep. Usually the quantity of spray required was
the same (3 to 5 gallons) as that for a residual treatment inside the barn.
Treatments were made every 3 to 7 days for 1 to 9 weeks at six dairies,
with oil solutions of chlordane, lindane, DDT, and methoxychlor.
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Most of the treatments, especially those with DDT plus methoxychlor,
gave a rapid knock-down of flies, and satisfactory control of the existing
adult fly population. The residual effect of the treatments was negligible,
however, as flies became numerous again in a few days. It was therefore
concluded that frequent spraying of premises had possibilities for control
in situations where other methods are inadequate, but that such treatments
would' be less practicable than residual or space spraying of the inside of
barns. It was also concluded that improved premises sanitation would be
necessary before dairymen could expect consistently satisfactory control
of flies from any type of insecticide application.
Additional premises-spraying tests were undertaken to compare the
effectiveness of a number of insecticides alone and in combination with
certain synergists. The materials tested included lindane alone and two
commercial formulations of lindane, one containing synergist RE -1901
and the other (RE -203 5) containing a trialkyl phosphate; DDT alone and
with synergists l,l-bis(chlorophenyl)ethane (K-3926) and chloro-
bis(p-chlorophenyl)methane (MR-60), and Santomerse DT (an N-alkylated
alkylene polyamine), Lauseto Neu (chloromethyl p-chlorophenylsulfone);
CS-708; and methoxychlor alone and with dimethyl phthalate. Lindane,
with and without synergists, was tested in kerosene solutions and emul-
sions, but all other materials only in emulsions. Applications were
made in the same manner as in 1950, but with only about half the volume
of spray. The reduction in volume was made possible by the use of a
fine-mist spraying unit developed by C. N. Husman. The results of
these tests are summarized in table 2.
Emulsion sprays of lindane plus synergist RE- 1901 gave excellent
control of house flies in all the dairies where they were applied. The
first application reduced fly populations 40 to 90 percent, and after
three to five applications at intervals of 2 to 3 days reductions of 90 to
99 percent were obtained. These results and incidental observations
indicated that the interval between treatments probably could be increased
to at least 4 to 5 days, particularly after the first week. Emulsions of
lindane alone gave good control in some dairies but only fair to poor con-
trol in others. An emulsion of lindane formulation RE-2035 was ineffec-
tive in one dairy. The kerosene solutions of lindane alone and with the
two synergists failed to give satisfactory control in any dairy, and in
most tests caused only negligible reductions in fly populations. The
reason for the wide difference in the effectiveness of the solutions and
emulsions was not determined.
DDT showed little toxicity alone and was only slightly more effective
when combined with Santomerse DT or K-3926. DDT plus synergist
MR-60 gave good control in one dairy but was ineffective in another.
Methoxychlor alone and combined with dimethyl phthalate, CS-708,
and Lauseto Neu caused little or no reductions in existing fly populations
and were totally lacking in residual toxicity (results not given in table).
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The flies from all the dairies were slightly to highly resistant to
lindane and highly resistant to DDT. Five of seven collections were
more susceptible to the lindane -synergist residue than to lindane alone,
but the other two were slightly more susceptible to lindane alone. All
the collections were far more susceptible to the DDT-synergist than
to DDT alone. In all cases, however, the LT-50 for the dairy flies
exposed to the DDT-synergist was considerably greater than for the
laboratory- colony flies, an indication that this combination would not
give effective control of the DDT-resistant flies in the dairies. This
was subsequently borne out by the failure of this combination to control
flies in field trials.
Neither synergist increased the effectiveness of the insecticide
against laboratory colony flies.
In 1951 residual and space-spray tests were conducted in dairies to
evaluate several chlorinated hydrocarbon insecticides alone and in com-
bination with certain synergists, for the control of resistant house flies
( Musca domestica L.). All the materials tested were relatively ineffec-
tive as residues, the longest period of control achieved being about 1
week with an emulsion of lindane plus synergist RE-1901 (2-hydroxy-
decachloro-4,7-methanoindane). The same material applied in emulsion
form as a mist spray twice each week to dairy barns and adjacent
grounds gave excellent control in every test and was superior to lindane
alone. Kerosene solutions of lindane with and without synergists were
relatively ineffective. Emulsions of toxaphene, methoxychlor, DDT,
Lauseto Neu (chloromethyl p-chlorophenyl sulfone), and CS-708 failed
to give satisfactory control.
(1) Gilbert, I. H. , Wilson, H. G. , and Coarsey, J. M.
1950. Control of house flies in barns with different insecticides.
U. S. Bur. Ent. and Plant Quar. E-795, 11 pp.
3 1262 09239 6281